1. Field of the Invention
The present invention relates to a sewing and more particularly to a sewing machine having a fabric-edge tracing function.
2. Description of Prior Art
Fabric-edge tracing sewing machines enabling formation of a seam at a position spaced a predetermined distance from an edge of a work fabric are generally known.
There is described in Japanese Patent Laid-Open No. 221389/1987, for example, corresponding to an application filed by the present assignee a fabric-edge tracing sewing machine designed to control a fabric-edge detector to follow a fabric edge and form a seam at a position spaced a set tracing width from an edge of a work fabric.
In case of carrying out a tracing sewing at a corner portion of a work fabric, an operator temporarily stops the tracing sewing in the vicinity of a mark formed at a predetermined position corresponding to a corner of a tracing line under the condition where a sewing needle is in a needle-down position, and then rotates the work fabric in a predetermined direction to restart the tracing sewing. In this case, when a tracing width at restarting of the tracing sewing does not accord with the set tracing width in the prior art edge tracing sewing machine, an error between both the tracing widths is so controlled as to be gradually corrected with several stitches after restarting the tracing sewing.
Since the error between both the tracing widths at the corner portion of the work fabric is gradually corrected with several stitches as mentioned above, a seam at the corner portion is partially curved. As a result, there are problems such that a corner portion of a collar front is not beautifully formed, for example, when turning the work fabric inside out, and the quality of a product executed by such tracing sewing is reduced, since the seam line does not accurately trace a fabric edge at the corner portion.